Method of partitioning blood using polyesters

ABSTRACT

A polyester is provided which facilitates the separation of blood into light and heavy phases via centrifugation in a blood collection vessel. The polyester is useful as a component of a partitioning composition formulated to have appropriate specific gravity to be positioned intermediate the light and heavy blood phases during centrifugation. A partitioning composition including a polyester of the invention provides a particular advantage in blood collection vessels due to its lighter and more consistent coloration. The polyester composition can be prepared with relative ease compared to prior art polyesters useful in blood partitioning compositions.

This application is a divisional application of Ser. No. 08/390,898,filed on Feb. 16, 1995, now U.S. Pat. No. 5,506,333, which is acontinuation of application Ser. No. 08/100,535, filed on Jul. 30, 1993,now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to polyesters useful for facilitating theseparation of blood serum or plasma from the cellular portion of blood.

2. Description of the Related Art

The polyesters of the invention are conveniently formulated into apartitioning composition for use in a blood collection vessel in whichthe blood sample is subjected to centrifugation until the cellularportion and serum or plasma are completely separated. The physical andchemical properties of the partitioning compositions are such that acontinuous, integral seal is provided between the separated bloodphases, thereby maintaining separation of the phases aftercentrifugation and simplifying removal of the serum or plasma from theblood collection vessel. The high volume testing of blood components inhospitals and clinics has led to the development of various devices tosimplify the collection of blood samples and preparation of the samplesfor analysis. Typically, whole blood is collected in an evacuated,elongated glass tube that is permanently closed at one end and sealed atthe other end by a rubber stopper having a diaphragm which is penetratedby the double-tipped cannula used to draw the patient's blood. After thedesired quantity of blood is collected, the collection vessel issubjected to centrifugation to yield two distinct phases comprising thecellular portion of the blood (heavy phase) and the blood serum orplasma (light phase). The light phase is typically removed from thecollection vessel, e.g., via pipette or decantation, for testing.

It has been proposed heretofore to provide manufactured, seal-formingmembers, e.g., resilient pistons, spools, discs and the like, in bloodcollection vessels to serve as mechanical barriers between the twoseparated phases. Because of the high cost of manufacturing such devicesto the close tolerances required to provide a functional seal, they havebeen supplanted by fluid sealant compositions. Fluid sealantcompositions are formulated to have a specific gravity intermediate thetwo blood phases sought to be separated, so as to provide a partition atthe interface between the cellular and serum phases. Such compositionstypically include a polymer base material, one or more additives foradjusting the specific gravity and viscosity of the resultantcomposition, and optionally, a network former. Representative prior artfluid sealant compositions include: styrerie beads coated with ananti-coagulant (U.S. Pat. No. 3,464,890); silicone fluid having silicadispersed therein (U.S. Pat. No. 3,780,935); a hydrophobic copolyesterincluding a suitable filler, e.g., silica (U.S. Pat. Nos. 4,101,422 and4,148,764); a liquid alpha-olefindialkylmaleate, together with analiphatic amine derivative of smectite clay or powdered silica (U.S.Pat. No. 4,310,430); the reaction product of a silicone fluid with asilica filler and a network former (U.S. Pat. No. 4,386,003); a mixtureof compatible viscous liquids, e.g., epoxidized vegetable oil andchlorinated polybutene, and a thixotropy-imparting agent, e.g., powderedsilica (U.S. Pat. No. 4,534,798); a thixotropic gel comprising a dualresin component including poly-alpha-pinene of lower density combinedwith chlorinated octadecene of higher density, said gel furthercomprising a radiation stabilizer, a network stabilizer, a thixotropicagent and a pigment (U.S. Pat. No. 4,994,393); and a gelatinous materialadmixed with fine resin particles having an average particle size of0.01 to 2 microns and having an internal crosslinking density of 0.1 to3 mmol/g (U.S. Pat. No. 5,169,543).

Ideally, a commercially useful blood partitioning composition shouldmaintain uniform physical and chemical properties for extended timeperiods prior to use, as well as during transportation and processing ofblood samples, readily form a stable partition under normalcentrifugation conditions and be relatively inert or unreactive towardthe substance(s) in the blood whose presence or concentration is to bedetermined. Inertness to substances sought to be determined is aparticular concern when blood collection vessels are used fortherapeutic drug monitoring (TDM), which is assuming an increasinglyimportant role. TDM is established through the accumulated experience ofclinicians, and consequently reduces the number of patients receivingdosage levels that are either below detection limits or toxic.Administration of drugs under TDM allows one to take into account suchfactors as drug tolerance developed with passage of time, presence ofmultiple physical disorders and synergistic or antagonistic interactionswith other therapeutic agents. Among the drugs recommended foradministration under TDM are those having dangerous toxicity with poorlydefined clinical endpoint, steep dose-response curve, narrow therapeuticrange considerable inter-individual pharmacokinetics variability ornonlinear pharmacokinetics, as well as those used in long term therapyor in the treatment of life-threatening diseases. By way of example, theevaluation of blood levels of a number of tricyclic antidepressantcompounds, such as imipramine or desipramine, in relation to anempirically established therapeutic range is reported to be particularlyuseful in the treatment of seemingly drug-refractive depression. TDM islikewise used to monitor the dosage of anficonvulsant drugs, such asphenytoin and phenobarbital which are administered in the treatment ofepilepsy, antitumor drugs, such as methotrexate, and other more commonlyprescribed drugs, including, but not limited to digoxin, lidocaine,pentobarbital and theophylline.

Reports of recent studies on the effect of blood partitioningcompositions on drug concentrations in serum and plasma indicate thatcare must be taken in the selection of polymeric materials which comeinto contact with the blood samples obtained for drug assay. See, forexample, P. Orsulak et al., Therapeutic Drug Monitoring, 6:444-48 (1984)and Y. Bergqvist et al. Clin. Chem., 3:465-66 (1984). The results ofthese studies show that the blood partitioning compositions provided inblood collection vessels may account for reduced serum or plasma values,as a result of drug absorption by one or more components of thecomposition. The reported decreases in measured drug concentrationsappears to be time-dependent. One report concludes that the observeddecreases in drug concentrations may effectively be reduced byminimizing the interval between collection and processing. Anotherreport recommends that blood samples be transported to the laboratory assoon as possible, with processing occurring within 4 hours. Acommercially useful blood collection vessel, however, must produceaccurate test results, taking into account routine clinical practices inlarge institutions, where collection, transportation and processing ofblood samples may realistically take anywhere from about 1-72 hours.

U.S. Pat. No. 4,148,764 teaches polyesters useful as a barrier materialin blood separation assemblies. The polyesters are comprised of thereaction products of essentially stoichiometric quantities of: (1) adicarboxylic acid component which is comprised of: (a) aliphaticdicarboxylic acid having from 4 to about 12 carbon atoms, (b) apolymeric fatty acid containing 75% by weight or more of a C36 dibasicacid; (2) a diol component which includes a branched-chain aliphaticdihydric alcohol having 3 to 8 carbon atoms, a mixture of these dihydricalcohols, or a mixture containing at least 50% by weight of thebranched-chain aliphatic dihydric alcohols and a straight-chainaliphatic dihydric alcohol having 2 to 8 carbon atoms. The equivalentsratio of (a) to (b) ranges from 0.80:0.20 to 0.97:0.03. The polyestershave an average molecular weight of 2,000-10,000, a kinematic viscosityat 210° F. of 2,000-8,000 centistokes, and a density in the range offrom 1.015 to 1.060 g/cm³ at 25° C.

U.S. Pat. No. 5,124,434 discloses polyesters useful in bloodpartitioning wherein the polyesters comprise at least four components,namely about one mole of a dicarboxylic acid member and one mole of adiol member wherein said acid member is comprised of a firstdicarboxylic acid component having from about 5 to about 60 mole percentof an aliphatic dicarboxylic acid having from 13 to about 22 carbonatoms, a second dicarboxylic acid component having from about 35 toabout 90 mole percent of an aliphatic dicarboxylic acid having from 4 toabout 12 carbon atoms, and a third dicarboxylic acid component havingfrom about 5 to about 25 mole percent of an aliphatic dicarboxylic acidhaving about 36 carbon atoms, said polyester being in the form of aviscous liquid and having a density at room temperature in the range of1.01-1.09. However, U.S. '434 does not suggest the use of dimer diol, a36 carbon atom dihydric alcohol, as a useful diol member. Also, there isno teaching that a polyester useful in functional blood partitioningcompositions having reduced affinity for therapeutic agents present inblood such as phenobarbital and imipramine can be prepared from onlythree ingredients. The ability to make fluid hydrophobic polyesters withprecise density control from three rather than four ingredients providesobvious advantages in terms of simplifying the manufacturing process fortheir preparation. Fewer reactants means there are fewer opportunitiesfor making errors in charging the reactants to the reaction vessel.Production efficiency is also improved due to the relatively high rateof polycondensation observed during the preparation of the polyesters ofthe instant invention. It has been observed that the dimer diolcontaining polyesters are lighter in color than the dimer acidcontaining polyesters taught in U.S. Pat. No. 5,124,434. The dimer diolapparently affords reduced susceptibility to thermal-oxidative darkeningunder the reaction conditions employed to prepare polyesters. Inaddition, when looking at batch to batch variability, the use of dimerdiol generates polyesters which have a more nearly constant color thanexhibited by the dimer acid containing polyesters. The lighter, and moreconsistent color of the dimer diol polyesters facilitates color matchingwhen those polyesters are employed in silica-polyester-stabilizerfunctional blood partitioning compositions.

British patent 685,649 discloses a process for the preparation ofpolyesters made by reacting succinic acid having an open chainhydrocarbon radical containing from 18 to 26 carbon atoms directlyjoined to at least one of the methylene groups and an organic compoundhaving two esterifiable hydroxyl groups.

U.S. Pat. No. 4,480,087 teaches polyester waxes which contain as theacid member at least 75 mole percent of alkylsuccinic anhydride oralkenylsuccinic anhydride and the acid functional derivatives thereof,and linear aliphatic and cycloaliphatic glycols having from 2 to 12carbon atoms as the diol member. The remaining acid member may be a C₄to C₁₀ dibasic aliphatic acid such as succinic or adipic acid. Thepatent does not teach polyester compositions incorporating a 36 carbonatom diol member, nor does it contain any suggestion that such polyestercompositions are useful as functional blood partitioning compositionshaving reduced affinity for therapeutic agents present in blood such asphenobarbital and imipramine.

U.S. Pat. No. 5,101,009 relates to copolyester resins which contain asthe acid member either terephthalic acid or a dialkyl terephthalate, andcontain as the diol member both a dimer diol and at least one glycolhaving 2 to 8 carbon atoms. The patent does not teach the use ofaliphatic diacids as the acid member, nor does it contain any suggestionthat such copolyester compositions are useful as functional bloodpartitioning compositions having reduced affinity for therapeutic agentspresent in blood such as phenobarbital and imipramine.

U.S. Pat. No. 5,176,956 discloses an improved biomedical appliancehaving disposed on a skin-contacting, operant portion thereof, a film orlayer of a skin compatible, tacky, pressure sensitive polymericadhesive, the reaction product consisting of at least on fatty aciddimer based or derived component, including dimer diol, and a suitableco-reactant, including dihydric alcohols. The patent does not containany suggestion that their polyester compositions are useful asfunctional blood partitioning compositions having reduced affinity fortherapeutic agents present in blood such as phenobarbital andimipramine.

SUMMARY OF THE INVENTION

In accordance with the present invention, it has been discovered thatcertain highly hydrophobic polyesters satisfy the above-noted criteriafor incorporation in a clinically useful blood partitioning composition.The polyesters according to the invention comprise a dicarboxylic acidmember and a diol member.

The diol member is comprised of dimer diol, a 36 carbon atom dihydricalcohol available from the hydrogenation of dimer acid, where dimer acidis produced by the dimerization of 18 carbon atom fatty acids. Thepolyester is in the form of a viscous liquid having a density at roomtemperature in the range of about 1.01 to about 1.09.

More particularly, the polyesters of the invention comprise as repeatingunits:

A=(--O--R_(A) --O--) and

B= ##STR1##

wherein R_(A) has 36 carbon atoms of the empirical formula:

    C.sub.36 H.sub.70

and R_(B) is a member selected from the group consisting of a divalentaliphatic chain of 1-34 carbon atoms, a divalent cycloaliphatic chain of3-34 carbon atoms, a divalent arylene chain of from 9-34 carbon atoms, adivalent alkarylene chain of from 7-34 carbon atoms, and a divalentalkarylene chain of from 8-34 carbon atoms and mixtures thereof.Alternatively, the polyester may comprise the following repeating units.

A=(--O--R_(A) --O--)

B= ##STR2## and

C=(--O--R_(C) --O--)

wherein R_(A) and R_(B) are as defined above.

and R_(C) is a member selected from the group consisting of compounds ofthe formula:

    R.sub.C =(CH.sub.n R.sub.m).sub.k

where

n=0, 1,2, or3

R=H, C₁ to C₁₀ alkyl

m=0, 1, or 2

n+m=2

_(k) =1 to 10

These include for example, 1,2 propylene glycol, 1,3 and 1,4 butanediol,3-methyl 1,5 penanediol and the like.

The incorporation of the C₃₆ dihydric aliphatic alcohol into thepolyesters of the present invention produces a product which, whenformulated together with other ingredients such as suitable filler andcompatible surfactant, is a functional blood partitioning composition.

The polyesters of the invention are readily formulated together withother ingredients, typically a suitable filler and compatiblesurfactant, into functional blood partitioning compositions. The densityof the finished blood partitioning composition is controlled withinprescribed limits, so that during centrifugation the composition becomesstably positioned at the interface between the serum or plasma phase andheavier cellular phase and, when centrifugation is terminated, forms acontinuous integral barrier within the blood collection vessel toprevent the two phases from recombining or mixing, especially whendecanting or pipetting the serum or plasma. The blood partitioningcompositions of the invention are advantageously employed in smallamount, on the order in a 10 ml blood collection vessel of the typepreviously described which are then ready for use in blood sampling andanalysis in the usual way. The polyester-based blood partitioningcompositions of the invention are especially suited for use in TDMprocedures, displaying negligible interaction with commonly monitoredtherapeutic agents.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polyesters according to the invention having the repeating units asset forth above, have molecular weights from about 3,000 to about 12,000(number average, as determined by gel permeation chromatography). Thepolyesters of the invention are produced in the form of viscous liquids,having a density at room temperature in the range of 1.01 to 1.09.Particularly notable among the properties of these polyesters is theirlight color and the batch to batch consistency of the polyestercoloration. Also notable among the properties of these polyesters istheir inertness, making them especially useful in TDM programs. Thepolyesters of the invention are also highly hydrophobic, exhibitingnegligible water solubility. The physical and chemical properties ofthese polyesters are uniformly maintained over extended periods prior touse, as well as during transportation and processing of blood samples.Among the other notable characteristics of these polyesters is theability to undergo ultracentrifugation for up to 1 hour at up to 1500G(G being the ratio of centrifugal acceleration to acceleration ofgravity), without any detectable adverse effect.

The polyesters of the invention are further characterized by having anacid value of 2 or less, an hydroxyl value of 25 or less and a 210° F.kinematic viscosity of about 1700-5000 centistokes.

Polyesters having the above-described properties are especially usefulas blood partitioning agents in blood collection vessels where theyprovide a continuous integral barrier or seal between the serum and clotportions of blood. In other words, the polyester completely partitionsthe separated phases so that the serum and cellular or clot portions areno longer in contact at any point, forming a unitary seal which firmlyadheres to the inner surface of the blood collection vessel. By forminga continuous, integral barrier in this way, it is possible to easilyremove the serum or plasma portion by decanting or pipetting, with theclot portion remaining undisturbed in the collection vessel.

As described above, the polyesters of this invention comprise adicarboxylic acid member and a diol member. Diacids suitable for use asthe dicarboxylic acid member include dicarboxylic acids of the formula:

    HOOC--R.sub.1 --COOH

where R₁ is a divalent alkylene chain having from 1 to 46 carbon atoms,and preferably is selected from the group consisting of divalentaliphatic chains of 1-34 carbon atoms, divalent cycloaliphatic chains of3-34 carbon atoms, arylene chains of from 6-34 carbon atoms, alkarylenechains of from 7-34 carbon atoms, and alkarylalkylene chains of from8-34 carbon atoms.

Suitable diacids useful in the practice of the present inventioninclude, but are not limited to oxalic acid, malonic acid, succinicacid, methylmalonic acid, fumaric acid, maleic acid, acetylenedicarboxylic acid, glutaric acid, ethylmalonic acid, dimethylmalonicacid, methylsuccinic acid, citraconic acid, glutasconic acid, itaconicacid, mesaconic acid, adipic acid, 2-dimethylsuccinic acid,3-methylglutaric acid, hydromuconic acid, muconic acid, pimelic acid,butylmalonic acid, diethylmalonic acid, 2-dimethylglutaric acid,2-ethyl, 2-methylsuccinic acid, 3-methyladipic acid,cyclopentanedicarboxylic acid, suberic acid, cyclohexanedicarboxylicacid, isophthalic acid, terephthalic acid, azelaic acid,5-norbornene-2,3-dicarboxylic acid, phenylmalonic acid, sebacic acid,camphoric acid, 1-cyclohexanediacetic acid, cyclohexylsuccinic acid,benzylmalonic acid, phenylene diacetic acid, phenylsuccinic acid,undecanedioic acid, 3-phenylglutaric acid, 1.10-decanedicarboxylic acid,4-phenylenedipropionic acid, naphthalene dicarboxylic acid,1.11-undecanedicarboxylic acid, 1.12-dodecanedicarboxylic acid,4-biphenyldicarboxylic acid, diphenic acid, hexadecanedioic acid, dimeracids and mixtures thereof. Especially preferred are adipic, azelaic,sebacic, and dodecanedioic acids.

It will be apparent to those skilled in the art that the variousart-recognized equivalents of the aforementioned dicarboxylic acids,including lower alkylesters and anhydrides and lower alkyl estersthereof, may be employed in preparing the polyesters of the invention.Accordingly, as used herein, the term "acid" is intended to encompasssuch acid derivatives. Methyl esters are particularly advantageous forthe preparation of the polyesters described herein. Mixtures of acids,anhydrides and esters may also be reacted to obtain the desired product.

The diol member of the polyesters of the invention comprises a dimerdiol, component having as a main component a compound of the formulaR_(A) as defined above.

These dimer diols are more fully described in U.S. Pat. No. 5,101,009which is incorporated herein by reference.

The diol member may additionally comprise one or more esterifiabledihydric compounds of the formula:

    HO--R.sub.C --OH

Representative diols falling within the foregoing formula includeneopentyl glycol, propylene glycol, diethylene glycol, triethyleneglycol, 3-methyl-1,5-pentane diol, 1,2 propane diol, 1,3-butane diol,1,2-butane diol, 1,2-pentane diol, 1,3-pentane diol, 1,4-pentane dioland the like. The diol member comprises dimer diol and propylene glycolwhere the molar ratio of dimer diol to propylene glycol charged to thereaction vessel ranges from about 0.17:0.99 to about 0.42:0.78.

Conventional esterification procedures and equipment are used to obtainthe polyester of the invention. The reactive components are normallyadded to the reaction vessel as a unit charge and the reaction mixtureis then heated with agitation at a temperature from about 150°-250° C.for a period of time sufficient to substantially complete theesterification reaction. The reaction may be driven to completion byapplication of vacuum (typically 1-5 mm Hg absolute at 200°-250° C.)until the desired properties are obtained. Vacuum distillation removesthe final traces of water, any excess reactants and small amounts ofother volatile materials present in the reaction mixture.

While the polyesters of the invention are formed with notably lightcoloration, if a further improvement in color is desired, the polyestermay be bleached by any of the well known and accepted bleaching methods,e.g., using hydrogen peroxide or chlorite. Alternatively, the polyestermay be decolorized by filtering through a filter aid, e.g., charcoal orbleaching clay.

The rate of esterification may be enhanced by the use of knownesterification catalysts. Suitable esterification catalysts forenhancing the rate of esterification of free carboxyl groups includephosphoric acid, sulfuric acid, toluenesulfonic acid, methane sulfonicacid, and the like. The amount of such catalyst may vary widely, butmost often will be in an amount from about 0.1% to about 0.5% by weight,based on the total reactant charge. Catalysts useful for effecting esterinterchange include dibutyltin diacetate, stannous oxalate, dibutyltinoxide, tetrabutyl titanate, zinc acetate and the like. These catalystsare generally employed in an amount ranging from about 0.01% to 0.05% byweight, based on the total resistant charge. When such catalysts areused, it is not necessary that they be present throughout the entirereaction. It is sometimes advantageous in order to obtain productshaving good color and relatively low acid value, on the order of 2 mgKOH/gm, or less, to add the catalyst during the final stages of thereaction. Upon completion of the reaction, the catalyst may bedeactivated and removed by filtration or other conventional means.

Inert diluents, such as benzene, toluene, xylene and the like may beemployed for the reaction. However, the use of diluents is notnecessary. It is generally considered desirable to conduct the reactionwithout diluents since the resultant polyester can be directly used asit is obtained from the reaction vessel. A small excess (based on theequivalents of acid present) of a volatile diol component may be used ifdesired. The excess diol serves as the reaction medium and reduces theviscosity of the reaction mixture. The excess diol is distilled off asthe esterification is carried to completion and may be recycled to thereactor if desired. Generally, about 20% by weight excess volatile diolwill suffice.

A particularly useful blood partitioning agent is obtained by reacting atotal of 1.0 mole of acid member which comprises adipic acid, with about1.2 moles of a diol member comprising dimer diol and propylene glycol.The molar ratio of dimer diol to propylene glycol ranges from about0.17:0.99 to about 0.42:0.78.

Preparation of blood partitioning compositions using the polyesters ofthe invention may be carried out in the manner described in commonlyowned U.S. Pat. Nos. 4,101,422 and 4,148,764, the entire disclosures ofwhich are incorporated by reference in the present specification, as ifset forth herein in full.

Determination of the extent of interaction between the polyesters of theinvention and commonly monitored drugs may be carried out using wellknown recovery experiments and drug measurement techniques, such as, gaschromatography, gas-liquid chromatography, high-performance liquidchromatography, thin layer chromatography or immunoassay techniques,including radioimmunoassay, enzyme immunoassay, fluorescencepolarization immunoassay, nephelometric assay, and the like. A varietyof suitable procedures are reported in the literature. See, for exampleBergqvist et at., supra. Such determinations may be carried out usinghuman serum, or commercially available bovine serum, if desired.

The following examples are presented to illustrate the invention morefully, and are not intended, nor are they to be construed, as alimitation of the scope of the invention. In the examples, allpercentages are on a weight basis unless otherwise indicated.

EXAMPLE 1

1.30 kilograms of a reaction mixture comprising adipic acid (Equivalentfraction 1.0, 41.91 wt. %), 1,2-propyleneglycol (Equivalent fraction0.75+20% excess, 19.63 wt. %), and dimerdiol (Equivalent ratio 0.25,38.46 wt. %, no excess used) was added in a 2-liter reaction flaskequipped with a mechanical stirring device, an electronic thermostat,and an insulated Vigreaux fractioning column leading into a recycle trapmounted underneath a reflux condenser, and heated gradually to a finaltemperature of about 225° C. The onset of esterification was observed asthe temperature reached about 190° when water began to accumulate in thetrap. The heating rate was adjusted to maintain the temperature of thecondensing vapors in the range 100°-110°, allowing the action of thefractionating column to return volatile glycol to the reaction vesselwith maximum efficiency. After about 8 hours, when about 85% of thetheoretical water of reaction had been collected, the apparatus wasevacuated, lowering the internal pressure by 28 inches of Hg. With thisdegree of evacuation and a reactor temperature of 225°, the conversionof acid groups to esters was essentially complete in 1.5 hours (totalelapsed time, 9.5 hours). A transesterification catalyst, namelydi-n-butyltin diacetate, was then introduced at a concentration equal to0.02% of the initial charge. The fractionating column was isolated fromthe system in favor of a shortened distillation path, and the apparatuswas evacuated to the maximum capacity of a "rough" laboratory pump (1-2mmHg). In about 0.75 hours, the viscosity rose to 3477 cSt @210° F. Thefinished product had an acid value of 0.4 mg KOH/g. and a hydroxyl valueof 20.7 (same units). Density of the polyester was 1.0266 gm./mL at 25°C.

While the present invention has been described and exemplified above interms of certain preferred embodiments, various other embodiments may beapparent to those skilled in the art. Accordingly, the invention is notlimited to the embodiments specifically described and exemplified, butvariations and modifications may be made therein and thereto withoutdeparting from the spirit of the invention, the full scope of which isdelineated by the following claims.

What is claimed is:
 1. A method of partitioning blood comprising thesteps of:(i) placing an effective amount of a polyester comprising therepeating units A and B of the formula:A=the group (-O--R_(A) --O--)from a dimer diol and B= ##STR3## wherein R_(A) has the empiricalformula:

    C.sub.36 H.sub.70

and R_(B) is a member selected from the group consisting of a divalentaliphatic chain of 1-34 carbon atoms, a divalent cycloaliphatic chain of3-34 carbon atoms, a divalent arylene chain of from 9-34 carbon atoms, adivalent alkarylene chain of from 7-34 carbon atoms, and a divalentalkaryalkylene chain of from 8-34 carbon atoms, and mixtures thereof, incombination with a filler and a compatible stabilizer, and optionally apigment into a blood collecting tube, (ii) introducing the blood to bepartitioned, and (iii) effecting the partitioning of the said bloodthrough the action of centrifugal force.
 2. The method of claim 1wherein R_(B) is a member selected from the group consisting of adivalent aliphatic chain of 3-34 carbon atoms, and said polyesterexhibits a room temperature density in the range of about 1.01-1.09, akinematic viscosity of about 1700 centistokes to 5000 centistokes at210° F., an hydroxyl value of 25 or less, and an acid value equal to 2or less.
 3. The method of claim 1 wherein said polyester comprises therepeating units A, B, and C of the formula:A=the group (--O--R_(A)--O--) from a dimer diol B= ##STR4## and C=(--O--R_(C) --O--) whereinR_(A) has the empirical formula:

    C.sub.36 H.sub.70

and R_(B) is a member selected from the group consisting of a divalentaliphatic chain of 1-34 carbon atoms, a divalent cycloaliphatic chain of3-34 carbon atoms, a divalent arylene chain of from 9-34 carbon atoms, adivalent alkarylene chain of from 7-34 carbon atoms, and a divalentalkaryalkylene chain of from 8-34 carbon atoms, and mixtures thereof,and R_(C) is a member selected from the group consisting of compounds ofthe formula:

    R.sub.C =(CH.sub.n R.sub.m).sub.k

wheren=0, 1, 2, or 3 R=H or a C₁ to C₁₀ alkyl m=0, 1, or 2 n+m=2 k=1 to10.
 4. The method of claim 3 wherein R_(B) is a divalent aliphatic chaincontaining 3 to 34 carbon atoms.
 5. The method of claim 3 wherein thepolyester has a hydroxyl value of less than 25 and an acid value of 2 orless.
 6. The method of claim 3 wherein in the polyester R_(B) is--(CH₂)₂ -- and R_(C) is --CH(CH₃)--CH₂ --.
 7. The method of claim 6wherein the molar ratio of R_(B) and the sum of R_(A) and R_(C) is inthe range of from about 0.9:1.1 to about 1.1:0.9.
 8. The method of claim6 wherein the molar ratio of R_(A) to R_(C) is in the range of fromabout 8:92 to 50:50.
 9. The method of claim 1 wherein the polyestercomprises about one mole of a dicarboxylic acid member and one mole of adiol member wherein said acid member is selected from the groupconsisting of compounds with two carboxylic acids moieties linked by analiphatic chain of 1-34 carbon atoms, a cycloaliphatic chain of 3-34carbon atoms, an arylene chain of from 9-34 carbon atoms, an alkarylenechain of from 7-34 carbon atoms, and an alkarylalkylene chain of from8-34 carbon atoms, or mixtures thereof, and wherein said diol member iscomprised of a first dimer diol component having 36 carbon atoms, and asecond dihydric alcohol component having the formula C=the group(--O--R_(C) --O--) from a dihydric alcohol wherein R_(C) is a memberselected from the group consisting of compounds of the formula:

    R.sub.C =(CH.sub.n R.sub.m).sub.k

wheren=0, 1, 2, or 3 R=H or a C₁ to C₁₀ alkyl m=0, 1, or 2 n+m=2 k=1 to10.
 10. The method of claim 9 wherein said acid member is selected fromthe group consisting of compounds with two carboxylic acids moietieslinked by an aliphatic chain of 3-34 carbon atoms.
 11. The method ofclaim 9 wherein the polyester has a hydroxyl value of less than 25 andan acid value of 2 or less.
 12. The method of claim 9 wherein in thepolyester the dicarboxylic acid member is adipic acid, and the seconddihydric alcohol component is propylene glycol.
 13. The method of claim12 wherein in the polyester the molar ratio of the dicarboxylic acidmember to the diol member is in the range from about 0.9:1.1 to about1.1:0.9.
 14. The method of claim 12 wherein in the polyester the molarratio of the first dimer diol component to the second dihydric alcoholcomponent is in the range of from about 8:92 to about 50:50.